But sometimes none of that seems like enough. It makes you want an additional solution, a pill that can boost you for long enough to get you over that hump.

While students and overworked employees frequently experiment with substances like Adderall or Ritalin in an attempt to do just that, it hasn't been shown that most of these "cognitive enhancers" actually make anyone's brain work "better."

But there's one substance that a recent review published in the journal European Neuropsychopharmacology found actually does improve attention, memory, learning, and other cognitive abilities — modafinil.

Pharmaceutical cognitive enhancement isn't a new idea. People have used drugs to try to boost their brainpower for more than 100 years. Early in his career in the late 1800s, Sigmund Freud experimented prolifically with cocaine, which he described at the time as his "most gorgeous excitement." Mathematician Paul Erdős had such a serious relationship with amphetamines that when he once stopped taking them for a month to win a $500 bet, he immediately got back on drugs afterwards. He famously told the friend he bet: "You've set mathematics back a month."

Those substances, however, come with significant negative side effects. That's what makes modafinil so interesting.

In their review of the literature on modafinil, Oxford researchers Ruairidh Battleday and Anna-Katherine Brem found that it didn't seem to have any particularly serious side effects and didn't seem likely to cause dependency — though there are still unanswered questions there.

How modafinil affects your brain

Battleday and Brem reviewed 24 studies that assessed how modafinil affected healthy non-sleep deprived people's minds (they considered 267 studies, but rejected those that weren't placebo controlled, used unhealthy subjects, or tested animals and not people). The fact that subjects were healthy is an important distinction — many of the ways we look at drugs that affect thinking ability are designed to assess people with cognitive deficiencies.

Most studies could be broken down into either "basic" or "complex" tests of cognitive function, Brem and Battleday tell Tech Insider.

Basic tests assess just one sub-component of cognition and tend to be very simple tasks. On these tests, the effects of modafinil were mixed. It was on complex tests that the authors found consistent improvement, especially in terms of attention, the ability to focus on a task and process relevant information; learning and memory; and executive function, which includes the ability to take in information and use it to come up with plans or strategies.

Films where characters suddenly gain access to new mental powers take the idea to an extreme, but cognitive enhancement is a real possibility.Universal

These complex tasks are much better ways to answer the question of "does this substance actually improve cognitive ability" than the basic ones, the authors tell Tech Insider.

"Rarely in life do we spend an entire day using a sole cognitive sub-domain - attention, for example. Rather, we constantly plan, predict, and problem solve - all of which involve marshaling subdomains of cognition and integrating their output - over varying tasks and difficulties," they wrote in an email. "It is in this sense that complex tasks can approximate everyday functioning better than simple."

As for how modafinil works, we still really don't know. It was originally designed as a treatment for narcolepsy to keep people awake. But no one is entirely certain how it affects cognition.

Matt Cardy/Getty

"The best idea we have is that by directly altering the concentration of a group of chemicals in the brain - called 'catecholamines' - modafinil upregulates activity in attention and executive control networks in the brain," the authors tell Tech Insider. "These changes are then hypothesized to allow individuals to perform better on cognitive tasks: particularly those requiring good focus and problem solving."

Can I take it?

So, will your doctor write you a modafinil prescription?

The answer for now is no, unless you have narcolepsy. But that may not always be the case.

When it comes to safety, Brem and Battleday said that the studies they reviewed didn't note serious side effects.

Most studies reported a slight boost to positive mood and no adverse effects. In the studies that found adverse effects, a small number of participants reported insomnia, headache, stomach ache or nausea, and dry mouth.

That may not sound great, but in context, those effects aren't such a big deal. That's essentially like having an extra cup of coffee that you didn't need, UCLA clinical psychiatrist James McGough told The Atlantic's Olga Khazan.

Only one study assessed the potential for abuse, and reported that it was low.

But none of these studies tested long term use, so we don't know if it's safe for someone to take modafinil over an extended period of time. As the authors point out, most of these studies only tested one single dose, which comes nowhere close to assessing risks of regular use.

Funding is scarce for drugs that help healthy people

Interestingly, Battleday and Brem point out that there isn't much research on cognitive enhancement for healthy people and that there's a lack of funding and perhaps even a bit of a taboo on studying the topic.

"It appears that funding for drug-based studies on healthy individuals fails to attract typically medical-oriented grants and awards," they say.

That's why they say it was hard to find good complex tests of cognitive enhancement, and they hope that perhaps their work will encourage researchers to further investigate the topic.

If that does happen, there may be surprises out there — perhaps some of the other drugs used for cognitive improvement, things like Adderall, work better for healthy people than we think they do despite their potential dependency risks.

But even if modafinil were to be proven safe long term and its cognitive boosting ability affirmed by further studies, there are still reasons why — for now — doctors aren't going to start prescribing it to healthy people.

At the recent annual meeting of the American Medical Association, the group decided to adopt a policy "discouraging the nonmedical use of prescription drugs for cognitive enhancement in healthy individuals."

There's little evidence so far that tells us how effective many other nootropics are or are not.
Dylan Love

Of prescription stimulants, they say that the cognitive effects appear limited for healthy people. Of other supplements and "smart drugs," known as nootropics, they say that there's limited research right now and that more analysis is needed before anyone can conclude that they are safe.

Will you someday be able to take the smart pill?

Let's say it turns out that multiple studies show that it's safe to take modafinil occasionally over long periods of time — for the rest of your life, even. Let's say that there are no additional negative side effects that come with that use.

If that's the case, should you be able to use the drug?

"That is a very interesting question, and one society must properly address in the near future; not just for modafinil, but for all potential neuroenhancement agents," say Battleday and Brem. But they point out that even if something proves to be safe for an individual, that doesn't answer all questions about how its use affects the rest of society.

A number of other devices might be able to stimulate the brain as well.
REUTERS/ Morris MacMatzen

Some people fear that if we permit any use of cognitive enhancing drugs for individuals, it will eventually lead to people being required to use those substances, even if they don't want to. That could be due to internal pressure that comes from a fear of keeping up — if my co-workers are taking this brain-boosting drug and I'm not, will I be judged as not working hard enough?

There's even a concern that people in certain professions might be compelled to use brain-enhancing substances. Could we get to the point that it's considered unsafe for pilots to fly or surgeons to operate without using focus- and attention-boosting drugs?

In The Conversation, researchers Emma Jane and Nicole Vincent describe how the use of beta-blockers became widespread among classical musicians. While some people first used these drugs to get over performance anxiety, they were so effective and had minimal enough side effects that other musicians felt they were losing out by not using beta-blockers as well.

"Just as the use of beta blockers has become widespread in the classical music scene, so too cognitive enhancement threatens to become a new 'normal', a de facto standard that pressures everyone to bio-hack their brains to keep up," they write.

And the ethical questions don't stop there. There are questions about justice — if wealthy people can easily afford cognitive enhancement but no one else can, that's likely to create an even more unequal society.

Cognitive enhancing substances are already out there and more are likely to become available in the near future. These questions about how to use them or how to regulate them are important.

"This is not a future but already a present scenario," say Brem and Battleday.